Valve stop changer tools are commercially available and are utilized extensively in gas distribution lines where it becomes necessary to change out a line valve without depressurizing the upstream service line in which the valve is contained. A physical requirement of such changer tools is that they be able to seal off the pipe upstream of the valve by means of a radially expandable plug which must first be passed through the valve ports from the downstream side of the valve. After the changer tool has been properly positioned and expanded for sealing engagement in the upstream pipe, the valve can be removed and replaced and/or repaired as necessary.
To the extent such changer tools are presently available, they are characterized by a limited expansion ratio in being custom matched by a manufacturer to the port geometries of valves marketed by that same manufacturer. As a result, such prior changer tools are generally unsuitable for valve port geometries manufactured by others. The customer, of course, much prefers for obvious reasons to have a changer tool with much more universal application than presently available to enable use with valves of different manufacture having different port geometries. Despite recognition of the problem, a ready solution therefor has not heretofore been known.